In a Long Term Evolution (LTE) system, Radio Resource Control (RRC) states of UE include an idle state and a connected state. When the UE is in the connected state, the UE performs uplink and downlink data transmission with a network side. When the UE is in the idle state, there is no data exchange between the UE and the network side. Because there is no data exchange between the idle-state UE and the network side, the network side cannot detect presence of the idle-state UE. In numerous existing scenarios, presence of the idle-state UE needs to be detected. For example, in an application such as crowd statistics collection or a thermodynamic diagram, a failure in detecting idle-state UE results in incomplete user statistics collection, and an application value is greatly reduced.